Starch Accumulation In Roots Research Articles

Morpho-Physiological and Biochemical Responses in Prosopis laevigata Seedlings to Varied Nitrogen Sources

Nitrogen (N) fertilization promotes morphofunctional attributes that enhance plant performance under stress conditions, but the amount and form supplied modify the magnitude of plant responses. We assessed several morpho-physiological and biochemical responses of Prosopis laevigata seedlings to a high supply of N, provided as either inorganic (NH4NO3) or organic (amino acids). Such N treatments were applied on four-month-old seedlings as a supplement of 90 mg N to a regular supply of 274 mg N plant−1. Nitrogen supply modified biomass allocation patterns between leaves and roots regardless of N form. Increased N input decreased photosynthetic capacity, even when plants had high internal N reserves. Organic N fertilization reduced the N use efficiency, but increased leaf and root amino acid concentrations. Proteins accumulated in stems in plants receiving inorganic N, while the organic N increased leaf proteins. High N supply promoted root starch accumulation irrespective of N form. Nitrogen supply did not directly influence plants’ regrowth capacity. Still, resprouting was correlated to initial root-to-shoot ratios and root starch, confirming the importance of roots as storage reserves of starch for recovering biomass after browsing. These findings have practical implications for designing nutritional management strategies in nurseries to improve seedling performance in afforestation efforts.

Formulation of the encapsulated rhizospheric Ochrobactrum ciceri supplemented with alginate for potential antifungal activity against the chili collar rot pathogen

The collar rot disease caused by the soil-borne fungus Sclerotium rolfsii (Sacc.) is a major constraint of chili (Capsicum annum L.) production in Pakistan. Considering the fact that biological control has low efficacy in field conditions, their encapsulation into biopolymers like alginate meets the essential criteria for bacteria viability, effectiveness, shelf life, stability, and controlled release. The current research was conducted to develop stable alginate beads of biocontrol bacteria (Ochrobactrum ciceri) and to check their efficacy in managing collar rot disease in C. annum. In vitro, antifungal bioassays indicated that increasing concentrations (16, 24, and 64%) of culture filtrate or the cell pellets significantly decreased fungal growth and enzyme activity (catalase: CAT, peroxidase: POX, polyphenol oxidase: PPO, and phenylalanine ammonia-lyase: PAL), hence increased offshoots hyphae, and caused distortion in sclerotia and hyphae. O. ciceri successfully developed stable alginate beads (AlgB-OC) as indicated by FTIR analysis, encapsulation efficiency (91.15%), moisture content (99.19%), swelling ratio (130%), particle size (wet: 2.11 mm; dry: 1.15 mm), film-forming time (48 h), and slow-release of entrapped bacteria till 30 days. AlgB-OC exhibited 76% antifungal potential in vitro and managed 70% of the collar rot disease in vivo. Moreover, the application of AlgB-OC significantly improved plant growth (length and biomass) and physio-chemical attributes (photosynthetic pigments, total protein content, activity of CAT, POX, PPO, and PAL), along with more lignin, phenolics, gel, and starch accumulation in roots. Multivariate analysis based on a total of 13 morpho-physiological indices of chili plants also identified AlgB-OC as the most effective treatment for disease management. It was concluded that the formulation of O. ciceri into alginate could be an effective alternative for managing collar rot disease in chili plants and obtaining better plant growth.

Gibberellin Promotes Sweetpotato Root Vascular Lignification and Reduces Storage-Root Formation.

Sweetpotato yield depends on a change in the developmental fate of adventitious roots into storage-roots. The mechanisms underlying this developmental switch are still unclear. We examined the hypothesis claiming that regulation of root lignification determines storage-root formation. We show that application of the plant hormone gibberellin increased stem elongation and root gibberellin levels, while having inhibitory effects on root system parameters, decreasing lateral root number and length, and significantly reducing storage-root number and diameter. Furthermore, gibberellin enhanced root xylem development, caused increased lignin deposition, and, at the same time, decreased root starch accumulation. In accordance with these developmental effects, gibberellin application upregulated expression levels of sweetpotato orthologues of Arabidopsis vascular development regulators (IbNA075, IbVND7, and IbSND2) and of lignin biosynthesis genes (IbPAL, IbC4H, Ib4CL, IbCCoAOMT, and IbCAD), while downregulating starch biosynthesis genes (IbAGPase and IbGBSS) in the roots. Interestingly, gibberellin downregulated root expression levels of orthologues of the Arabidopsis BREVIPEDICELLUS transcription factor (IbKN2 and IbKN3), regulator of meristem maintenance. The results substantiate our hypothesis and mark gibberellin as an important player in regulation of sweetpotato root development, suggesting that increased fiber formation and lignification inhibit storage-root formation and yield. Taken together, our findings provide insight into the mechanisms underlying sweetpotato storage-root formation and provide a valuable database of genes for further research.

How root traits would be affected by soybean yield improvement? An examination of historical cultivars grafted with record-yield cultivar scion

During historical yield improvement in soybean, breeders have seldom considered selection for root traits, generally focusing selection on yield traits. Yet, it is not known how root traits of historical cultivars would be altered if their shoot functions and grain yields were largely improved. Here we investigated the influence of record-yield soybean cultivars L14 and Z35 as scions on root traits of historical cultivars. A total of 11 cultivars, released in different decades, were used to graft with L14 or Z35 scions. Some morphological and physiological traits were measured in the pot-culture experiments. During grain-filling stage, the scions of L14 and Z35 had greater photosynthetic capacity, seed biomass and seed starch accumulation than those of other cultivars. Grafting of cultivars with L14 and Z35 scions resulted in significant decreases in root biomass, root-shoot ratio, root starch accumulation and root morphological traits compared with non-grafts or self-grafts. The genetic gain for these root traits of cultivars released from 1966 to 2006 increased by grafting record-yield cultivars scions, while that of grain yield and nutrient accumulation decreased. Our results revealed the uncoordinated improvement between roots and shoots during historical breeding in soybean.

Starch Concentrations in Grapevine Leaves, Berries and Roots and the Effect of Canopy Management

Diurnal and seasonal starch changes in leaves, berries and roots of Vitis vinifera L. cv. Cabernet Sauvignon/99 Richter and the effect of canopy management (a combination of suckering, shoot positioning, and 33% defoliation) on these processes were investigated under field conditions. An increase in starch concentration of basal leaves occurred from the morning to the afternoon during the most active vegetative growth period (up to veraison), indicating a proportional change in storage or export of assimilates between day and night. During later developmental stages diurnal starch levels slightly declined or remained the same. Seasonally, leaf starch remained relatively stable until veraison, whereafter it increased, reaching highest concentrations at the post-harvest stage. Canopy management generally increased leaf starch concentrations. Berries contained no significant amounts of starch. Root starch concentrations were usually higher than those of leaves. Diurnally as well as seasonally, root starch accumulation patterns coincided with those of leaves, indicating a close relationship between source and sink tissue. Canopy management resulted in stable diurnal root starch concentrations without affecting the daily mean starch level; afternoon values of treated vines were, however, generally lower. The results imply that carbohydrate supply and starch-synthesising enzyme systems were not limited by manipulating the canopy and decreasing foliage. It seems, however, that particularly late in the season starch accumulation in roots may be delayed by canopy manipulation as applied. This indicates a shift in sucrose partitioning and its utilisation in roots and other sink areas, e.g. the berries, when the canopy is manipulated.

Characters related to higher starch accumulation in cassava storage roots.

Cassava (Manihot esculenta) is valued mainly for high content starch in its roots. Our understanding of mechanisms promoting high starch accumulation in the roots is, however, still very limited. Two field-grown cassava cultivars, Huanan 124(H124) with low root starch and Fuxuan 01(F01) with high root starch, were characterised comparatively at four main growth stages. Changes in key sugars in the leaves, stems and roots seemed not to be strongly associated with the final amount of starch accumulated in the roots. However, when compared with H124, F01 exhibited a more compact arrangement of xylem vascular bundles in the leaf axils, much less callose around the phloem sieve plates in the stems, higher starch synthesis-related enzymatic activity but lower amylase activity in the roots, more significantly up-regulated expression of related genes, and a much higher stem flow rate (SFR). In conclusion, higher starch accumulation in the roots results from the concurrent effects of powerful stem transport capacity highlighted by higher SFR, high starch synthesis but low starch degradation in the roots, and high expression of sugar transporter genes in the stems. A model of high starch accumulation in cassava roots was therefore proposed and discussed.

English

The effects of auxin and the endogenous levels of reserve compounds of Phalaenopsis amabilis (L.) Blume (Orchidaceae) were analyzed in vitro. Rootless plants were inoculated in modified MS media supplemented with IBA or NAA (0.0, 0.2, 1.0 and 5.0 mg L-1) and with 2,4-D (0.000, 0.032, 0.160 and 0.800 mg L-1). The biochemical parameters of endogenous levels of soluble carbohydrates and starch and of total soluble protein in roots, leaves and shoots were analyzed after 30 and 120 days. Carbohydrate levels in leaves showed similar patterns for all treatments. At 30 days, there was an increase in the endogenous carbohydrate level along with an increase in the concentration of auxins. At 120 days, the endogenous carbohydrate level in leaves had decreased, while the auxin concentration had continued to increase, demonstrating the mobilization of the carbohydrates. The leaf carbohydrate levels decreased from day 30 to 120; for both IBA and 2,4-D treatments, there was starch accumulation in roots as a function of the collection date. The 2,4-D concentration of 0.0032 mg L-1 decreased the level of total soluble protein in roots. The in vitro plants exhibit different growth patterns depending on the classes and concentrations of growth regulators. Biochemical analyses exhibited that metabolic activity and the degradation and accumulation of substances occurs in leaves, roots and shoots, demonstrating that roots contribute to the maintenance of plant metabolism and also act as reserve organs, even in epiphytic plants.   Key words: Storage compounds, soluble carbohydrates, starch, soluble proteins.

Carbohydrate and Nutritional Responses to Stem Girdling and Drought Stress with Respect to Understanding Symptoms of Huanglongbing in Citrus

The most important worldwide problem in citrus production is the bacterial disease Huanglongbing (HLB; citrus greening) caused by a phloem-limited bacterium Candidatus Liberibacter asiaticus. The earliest visible symptoms of HLB on leaves are vein yellowing and an asymmetrical chlorosis referred to as “blotchy mottle,” thought to be the result of starch accumulation. We tested the hypothesis that such visible symptoms are not unique to HLB by stem girdling 2-year-old seedlings of two citrus rootstocks with and without drought stress in the greenhouse. After 31 days, girdling had little effect on shoot growth but girdling increased the relative growth rate of shoots in drought-stressed trees. Starch content in woody roots of non-girdled trees was three to 19 times higher than in girdled trees. In non-girdled trees, drought stress induced some starch accumulation in roots, but there were no effects of drought stress on root starch or sucrose in girdled trees. Girdling induced a 4-fold greater starch content in leaves on well-watered trees but leaf sucrose content was unaffected. Girdling reduced leaf transpiration in well-watered trees but net assimilation of CO2 was unaffected by girdling or leaf starch accumulation. Leaves on girdled trees clearly had visible blotchy mottle symptoms but no symptoms developed on non-girdled trees. The increase in leaf starch, up to 50% dry weight (DW), resulted in an increase in leaf DW per leaf area (LA) and an artificial reduction of many leaf nutrients on a DW basis. Most of these differences disappeared when expressed on a LA basis. Leaf boron (B), however, was inversely related to leaf starch when both were expressed on a LA basis. In the absence of HLB, girdling increased leaf starch, decreased root starch, and duplicated the asymmetric blotchy mottled visual leaf symptoms that have been associated with HLB-infected trees. This supports our contention that such symptoms generally attributed to HLB are not uniquely related to HLB infection, but rather are directly related to starch accumulation and secondarily to nutrient deficiencies in leaves.

Root starch accumulation in response to arbuscular mycorrhizal colonization differs among Lotus japonicus starch mutants

Arbuscular mycorrhizal (AM) fungi are obligate symbionts dependent for completion of their life cycle on plant carbohydrates, which they trade for mineral nutrients. Plant colonization by AM fungi is therefore expected to induce profound changes in plant carbon metabolism. We have previously observed that on one hand starch accumulation increases in responses to pre-symbiotic fungal signals and on the other hand, it decreases in mycorrhizal Lotus japonicus roots (Gutjahr et al. in New Phytol 183:53-61, 2009). To examine the importance of starch metabolism for AM development, we took advantage of a novel series of Lotus japonicus mutants impaired either in starch degradation or in synthesis. Normal AM colonization in all mutants indicated that defects in starch metabolism do not affect AM development and that carbohydrates can be supplied to the AM fungus without a requirement for starch synthesis. Furthermore, our experiments allowed us to characterize root starch dynamics in detail and point to continued turnover of starch in the degradation mutants in the presence of mycorrhiza.

Relationships between Leaf and Stem Soluble Sugar Content and Tuberous Root Starch Accumulation in Cassava

The purpose of this study was to examine the relationships between the soluble sugar content in the leaves and stems and the starch accumulation in the tuberous roots of four cassava cultivars: FuXuan01, GR891, SC124, and SC201. The results showed that the highest leaf soluble sugar content was in September, and the highest stem sugar content was in October, which played an important role in starch accumulation in the tuberous roots. The leaf and stem soluble sugar content and the tuberous root starch accumulation were positively correlated in the setting and growth stages but negatively correlated in the ripening stage. The soluble sugar content in the leaves went from high to low as the tuberous roots progressed from the setting stage to the ripening stage; starch accumulation in the root tubers followed the opposite pattern.

Nitrogen deposition limits photosynthetic response to elevated CO2 differentially in a dioecious species

Sexual dimorphisms of dioecious plants are important in controlling and maintaining sex ratios under changing climate environments. Yet, little is known about sex-specific responses to elevated CO(2) with soil nitrogen (N) deposition. To investigate sex-related physiological and biochemical responses to elevated CO(2) with N deposition, Populus cathayana Rehd. was employed as a model species. The cuttings were subjected to two CO(2) regimes (350 and 700 μmol mol(-1)) with two N levels (0 and 5 g N m(-2) year(-1)). Our results showed that elevated CO(2) and N deposition separately increased the total number of leaves, leaf area (LA), leaf mass, net photosynthetic rate (P(n)), light saturated photosynthetic rate (P(max)), chlorophyll a (Chl a), and chlorophyll a to chlorophyll b ratio (Chl a/b) in both males and females of P. cathayana. However, the effects on LA, leaf mass, P(n), P(max), Chl a and Chl a/b were weakened under the combined treatment of elevated CO(2) and N deposition. Males had higher leaf mass, P(n), P(max), apparent quantum yield (Φ), carboxylation efficiency (CE), Chl a, Chl a/b, leaf N, and root carbon to N ratio (C/N) than did females under elevated CO(2) with N deposition. In contrast to males, females had significantly higher levels of soluble sugars in leaves and greater starch accumulation in roots and stems under the same condition. The results of the present work imply that P. cathayana females are more responsive and suffer from greater negative effects on growth and photosynthetic capacity than do males when grown under elevated CO(2) with soil N deposition.

Dynamics of non-structural carbohydrate reserves in pruned Erythrina poeppigiana and Gliricidia sepium trees

In alley cropping systems, fast growing leguminous trees are pruned to reduce competition with crops for light and to provide organic inputs for crop nutrition. Tree regrowth depends on non-structural carbohydrate reserves in the remaining tree parts. In this study, the dynamics of starch and soluble carbohydrates in roots and stems of completely pruned (all shoots removed), partially pruned (one branch retained on the pruned stump) and unpruned Erythrina poeppigiana (Walp.) O.F. Cook and Gliricidia sepium (Jacq.) Kunth ex Walp. trees were studied under humid tropical conditions in Turrialba, Costa Rica. Measurements on starch and soluble carbohydrates in roots and stems were made at 0, 2, 6 and 12 weeks after pruning during both a “rainy” and a “dry” season. In general, the dynamics of non-structural carbohydrates in roots and stems of pruned E. poeppigiana and G. sepium trees were similar. Starch concentration was highest in unpruned trees and higher in roots than in stems of pruned trees. The effect of pruning intensity was first observed in stems, and starch reserves were more depleted in stems than in roots, an effect more evident during the “dry” season. The critical tree regrowth stage for starch mobilisation was that of vigorous sprout development at six or four weeks after pruning particularly in completely pruned trees. At this time, fine root biomass and length and nodule biomass in pruned trees decreased. Survival of fine roots and nodules was greater in partially pruned than in completely pruned trees. Starch accumulation in roots recommenced at 12 weeks after pruning in G. sepium, and later than 12 weeks after pruning in E. poeppigiana roots. This study showed that E. poeppigiana responded better to pruning regimes than G. sepium. Recovery of trees after pruning is better when trees are partially pruned than when completely pruned.

ROOT ZONE TEMPERATURE EFFECT IN HYDROPONICALLY GROWN CUCUMBER PLANTS: GROWTH AND CARBOHYDRATE METABOLISM

To investigate the effect of root zone temperature (RZT) on growth and carbohydrate metabolism in hydroponically grown cucumber plants, growth parameters and major carbon metabolites in plant tissues were analyzed at 2, 4, and 6 weeks after start of the RZT treatment (10°C, 18°C or 26°C). Shoot growth significantly increased with increasing RZT but not root growth until 4 weeks. Root activity at 18°C and 26°C continuously increased throughout the experimental period, while that at 10oC sharply decreased after 4 weeks. Chlorophyll content was less affected by RZT. The amount of hexose phosphate increased as RZT was lowered. Glyceraldehyde-phosphate (PGA) slightly increased within 18°C, but greatly fell down at 26°C RZT. Higher accumulation of soluble sugars was generally observed in both leaves and roots grown at 10°C RZT. Low RZT significantly depressed starch synthesis in leaves, but stimulated starch accumulation in roots.

Activity of the yeast mevalonate kinase promoter in transgenic tobacco

The coding region of the yeast mevalonate kinase gene ( ERG12) under the control of the cloned 564 bp promoter was introduced in tobacco ( Nicotiana tabacum cv. Paraguay Bell) using an Agrobacterium tumefaciens binary vector system. In this study, we provide evidence that the ERG12 promoter is sufficient to direct MK expression in agrobacteria and in plant cells. The tissue-specific pattern of expression directed by the ERG12 promoter was investigated by analysis of β-glucuronidase (GUS) activity in tobacco. A preferential expression of a ERG12-GUS fusion gene was observed in fast dividing cells of calli during regeneration and in meristematic tissues such as root-tips, lateral root primordia and the shoot apexes of growing plantlets. Histochemical tests and measurements of MK activity emphasize a temporal regulation of MK expression, leading to phenotypical modifications: acceleration of regenerating processes, peculiar flowering and starch accumulation in roots. Taken together, these results provide additional clues as to the possible functional role of MVA derivatives (i.e. some cytokinins or prenylated proteins) in cell cycle control.

Accumulation of starch in roots and foliage of loblolly pine (Pinus taeda L.): effects of season, site and fertilization.

Accurate predictions of stand response to nitrogen fertilization require a better understanding of the plant processes associated with stand nutrition. This study examined the relationship between stand nutrition and starch accumulation in roots and foliage of loblolly pine (Pinus taeda L.). A field study was located on the lower Coastal Plain of North Carolina on four sites of differing soil types. Stands of 8-year-old trees were fertilized with nitrogen (225 kg ha(-1)) or nitrogen plus phosphorus (225 kg N ha(-1) + 75 kg P ha(-1)) in 1981. Roots and foliage were collected from five trees per plot at six sampling dates from July 1983 through January 1985 and analyzed for starch. Starch concentrations showed seasonal fluctuations, with levels generally highest in early spring prior to budbreak. Root starch concentrations were lowest in autumn, whereas foliar concentrations were lowest in winter.